When comparing SciTE vs Codiad, the Slant community recommends SciTE for most people. In the question“What are the best programming text editors?”SciTE is ranked 13th while Codiad is ranked 52nd. The most important reason people chose SciTE is:

Based on the Scintilla source code editor, SciTE has some advanced features like rectangular editing, simple regular expression search and replace, code folding, etc. It allows the user to launch a compiler or interpreter, and it can also interpret the error messages, jumping at the location they point to.
Lua scripting is key to SciTE's power and flexibility. The Lua scripting language can be used to perform complex text transformations. It's relatively simple syntax and its large user-base makes it a great choice for a scripting feature.

Pros

Pro

Powerful

Based on the Scintilla source code editor, SciTE has some advanced features like rectangular editing, simple regular expression search and replace, code folding, etc. It allows the user to launch a compiler or interpreter, and it can also interpret the error messages, jumping at the location they point to.

Lua scripting is key to SciTE's power and flexibility. The Lua scripting language can be used to perform complex text transformations. It's relatively simple syntax and its large user-base makes it a great choice for a scripting feature.

Pro

Flexible

It's property files allow for fine tweaks of its behavior, at a global or per language / project level. These textual settings might be confusing for those used to preference dialogs, but prove to be powerful, flexible, and fine grained.

Pro

Lightweight

With less than 2 MB of binary on Windows, SciTE starts instantly. Plus, if you don't need all the config, syntax files, blah, there's a 678k standalone .exe version. Nothing is going to beat that for lightweight and start-up times. Stick it in a folder that is already on your PATH.

Pro

Built-in shell

The console window can show the result of ran commands (like build current file, reporting warnings, and errors), but also accept interactive shell commands.

Pro

Portable

SciTE works on Windows and Linux, and it also has a commercial port on MacOS.

Pro

Powerful syntax highlighting for numerous languages

Lexers providing folding and syntax highlighting are based on code, not on regular expressions. They support context, nesting, special rules, etc.

Pro

Free (except on Mac) and open source

SciTE is written in C++, with lot of contributors, both to the core and to the numerous lexers.

Pro

GUI

Has a simple graphical user interface

Pro

Multi-line edit

Allows to edit multiple things are once by having multiple cursors like Sublime Text.

Pro

Easy to self-host: Only requires PHP

It only requires PHP 5+ and Nginx or Apache. No database is required. This makes it really easy to install on many servers include shared hosting.

Pro

Has many easily installable plugins

Many plugins exist, from Terminal, Git to Collaboration and Emmet... Plugins can be installed by using the web interface, or by manually extracting files to the right directory.

Pro

Open source

You can run Codiad on your server to allow you and your team to edit files.Simplest to run may be using a Docker image like linuxserver/codiad.

Pro

Simple and easily managable GUI

Cons

Con

Hard to config

The configuration is mainly a file-based config, which can be unintuitive and difficult to use for new users.

Con

Missing file browser

SciTE's greatest weakness is perhaps the file browser. It does not really have one, just a poor substitute which works a little bit like a terminal window with ls or dir commands to show the files in a directory.

Con

Customization

No extensions, Themes.

Con

Full of small bugs

There are plenty of various issues and bug that may either be due to your setup and the UI will not report them, or due to bugs in the code; I'm including common plugins here as well (just naming a few: search files and in files may report nothing if it had an error, commands stderr not printed, marketplace not showing items, search in market place showing no results, Git escaping ( by \( in the commit message for no good reason...). Those are generally small but together it makes the product feel flawed.

Con

Terminal runs as same user for everyone

No matter who is the logged in user, the Terminal plugin runs commands as the PHP user. This also affects the Git plugin in that there is a single SSH key for all users using your Codiad instance.

Con

Currently no search and replace in multiple files

There is a search in multiple files, and search & replace in current file, but not something to perform a search & replace in multiple files.

Con

Terminal doesn't TTY

The terminal plugin for Codiad allows users to type some commands and see the outputs, but not interactive input is supported (i.e. stdin is closed). Meaning you cannot run Vim, Tmux or anything requiring user inputs.